This invention concerns flow sensors for sensing flow of fluids such as lubricants or grease, and more particularly concerns a device for sensing flow of quantities of volumetric metered lubricant in locations remote from the fluid delivery source, particularly where the quantities are small and must be delivered in rapid succession.
Reed switches are commonly used in flow sensors to detect movement of a flow sensitive member such as a piston. However, reed switches require relatively long movements of sixty thousandths of an inch or longer, which results in an undesirably slow response time and resultant slow cycle time. Also, the reed switches may be difficult and messy to replace, and fine adjustment of the reed switch is often not easily accomplished. Further, the pistons commonly used with reed switches in remote flow sensors include close tolerances, and may hang-up or bind on particles and contaminants in the fluids, lubricants or grease. Still further, as the remote flow sensors are adjusted for maximum sensitivity to deliver very small quantities of lubricant, known flow sensors often give false signals to the controller of the fluid delivery source, causing disruption of the product process or too much fluid to be delivered.
Therefore, a flow sensor solving the aforementioned problems is desired.